I put hair and scalp. I normally concentrate on my scalp more and then at the last minute I'll do a quick shampoo on the rest.
I just can't stand for my hair to have any type of unpleasant odor, whether its from food(you know how when you cook the aroma sticks to your hair), being around cigarette smoke(alhtough with the new smoking bans thats become less of a problem), or being outside and getting that gross sweat smell(probably more of a living in Florida problem).
Anyway, I have to smell clean head to toe so when it comes to shampoo everything gets it!